Wastewater Solutions

Last updated: September 2026

Reviewed by: Online Tank Store Technical Team

Choosing the right wastewater system is essential for safely and effectively managing wastewater from your property. At The Online Tank Store, we offer a comprehensive range of wastewater solutions to suit a variety of properties, site conditions and requirements.

From cesspools and septic tanks to pump stations and sewage treatment plants, our range provides reliable solutions for properties that aren’t connected to mains drainage. Whether you need a simple wastewater storage solution or a complete treatment system, our buyers guide can help you understand the options available and choose the right solution for your needs.

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What are wastewater systems and why may I need one?

Wastewater systems are designed to safely collect, treat, store and dispose of wastewater from homes and other properties. They are particularly important for properties that are not connected to the mains sewer network, such as rural homes, holiday lets, campsites, commercial premises and properties in remote locations.

There are several types of wastewater systems available, including septic tanks, sewage treatment plants, cesspits and pump stations. Each system works differently and is suited to different site conditions and requirements. The right option will depend on factors such as the number of people using the property, the amount of wastewater produced, ground conditions and how the treated or stored wastewater can be discharged.

A suitable wastewater system provides a reliable, hygienic and environmentally responsible way to manage wastewater, while helping your property comply with relevant regulations. Choosing the correct system from the outset can also help reduce maintenance requirements and ensure effective long-term performance.

Quick Answer Box

✔ No suitable place for discharging sewage → Cesspools

✔ Available drainage field for discharging effluent → Septic tanks

✔ High pollutant removal levels → Sewage treatment systems

✔ Strict requirements for discharging sewage → Sewage treatment systems

✔ Gravity drainage not possible → Pump stations

Quick Facts

✓ Our range currently available for everything from single households to commercial sites accommodating up to 50 people

✓ Suitable for domestic, agricultural, commercial and industrial applications

✓ The Harlequin Hydroclear range has the market leading pollutant removal – 97.5%

✓ We can arrange free site visits to ensure we find the right system for you

✓ All sewage treatment plants come with an external blower for optimal performance

Types of wastewater systems

There are several wastewater systems available, each designed to meet different property and site requirements. Cesspools, septic tanks, sewage treatment plants and pump stations each provide a different approach to wastewater storage, treatment and disposal. From simple storage solutions for properties without mains drainage to advanced treatment systems for domestic and commercial applications, choosing the right system depends on factors such as occupancy, wastewater volumes, site conditions and discharge requirements.

Cesspools

Suitable for: Properties without a mains sewer connection or a suitable outlet for sewage discharge. Cesspools are particularly suited to remote locations and low water-use properties.

View Cesspools

Pump stations

Suitable for: Ideal for properties where wastewater cannot flow away by gravity alone. Pump stations collect and temporarily store wastewater before pumping it to a higher-level drainage system, treatment plant or discharge point.

View Pump stations

Septic tanks

Suitable for: Ideal for properties without access to a mains sewer connection, but with a suitable drainage field for the discharge of treated effluent.

View Septic tanks

Sewage treatment plants

Suitable for: Ideal for properties without access to a mains sewer connection, where a higher level of wastewater treatment is required before the treated effluent can be discharged to a suitable watercourse or drainage field.

View Sewage treatment plants

Washdown separators

Suitable for: Ideal for commercial and industrial sites where washdown water may contain oils, fuels, silt or other contaminants. Washdown separators help treat and separate pollutants before wastewater is discharged to a suitable drainage system or watercourse.

View Washdown separators

Cesspools

Cesspools are sealed underground storage tanks that collect and store sewage and wastewater. They require emptying by a licensed waste contractor and should be emptied whenever they are nearing capacity.

Cesspools are recommended where there is no connection to the mains sewage system and there is no suitable drainage field or watercourse for wastewater to be discharged into.

Capacity options:

1800 Litre

2600 Litre

3400 Litre

Lid options:

Pedestrian duty lockable cover

This is suitable for when the cesspool is located where no vehicles will need to pass over the tank. It is suitable to withstand pedestrians walking on the lid and is rated to carry a weight up to 200kg.

The underground cesspools are designed for shallow-dig installation with a pea gravel surround. However, the installation can be modified to allow vehicles to drive over the tank where required.

Light vehicle cover

This strengthened lid can withstand a passenger car type vehicle driving over it and is rated to carry a weight up to 600kg. This means that the lid needs to be protected from trucks and heavy goods vehicle traffic.

Although the vehicle lid itself is designed to withstand a load of up to 600 kg, the tank itself is not designed to withstand vehicle loading. The vehicle lids are primarily intended to provide access to the tank when it needs to be emptied or cleared by a vehicle.

Emptying requirements:

As a rough guide, cesspools may require emptying:

For 2–4 people: every 4–8 weeks
For larger households: every 2–4 weeks

These timeframes are approximate and can vary depending on the size of the cesspool and the volume of wastewater produced.

View all Cesspools here

Optional extras:

High-level alarms – are optional extras, these are mains operated and warns you when the tank needs emptying

Telescopic extension risers – allow the depth of the tank to be increased to between 400 and 750mm. This can be easily trimmed by using a hand saw.

Backflow Non-return valves – are used to prevent flooding of tanks or buildings from sewage that may travel back up the pipework system.

Pump stations

Pump stations provide a solution for moving sewage and wastewater where gravity is not possible. Pump stations are installed underground and pumps wastewater to a higher-level sewer, treatment plant or other suitable discharge point.

Capacity options:

450 Litre

For single person dwellings

800 Litres

For 1 – 5 Persons

1100 Litres

For 1 – 7 Persons

1550 Litres

For 1 – 10 Persons

2700 Litres

For 1 – 18 Persons

3200 Litres

For 1 – 21 Persons

There are 3 pump variations:

Effluent pumps

these are drainage pumps and are suitable for following a treatment plant, septic tank or moving surface water. These ones are not suitable for pumping raw sewage.

Sewage pumps

these are solids handling vortex pumps , they pump sewage up to a treatment plant or other suitable discharge point. It is important that ONLY sewage and toilet paper are flushed when using these pump stations.

Grinder pumps

these are also solids handling pumps for sewage, however, these are more accommodating for sites where you have less control over what is being flushed. For example, public toilets, campsites or rental properties

You have the choice of single or twin pumps:

Single pumps

Single pump stations come with one submersible pump with integrated float switch. It is recommend to have a high level alarm fitted – this will indicate when the water or sewage limit has risen above the safe operating levels.

Twin pumps

Twin pump stations come with 2 submersible pumps and a high-level alarm as standard. The twin pump station provides increased reliability and continued operation should one pump experience a fault. (all pump sizes, other than the 450 Litre, have the option of a twin pump)

View all Pump stations here

Optional extras:

High-level alarms – are optional extras for the single pumps, however, these come as standard with the twin pumps.

The high-level alarm indicates when the water or sewage limit has risen above safe operating levels

Septic tanks

Septic tanks provide an effective solution for managing sewage, treating wastewater while retaining solid waste. Where mains drainage is unavailable, a septic tank connected to a soakaway system offers a reliable and practical wastewater solution. All our septic tanks comply with the required regulations and are manufactured to provide long-lasting performance.

Capacity options:

2600 Litre

For up to 4 person

3400 Litres

For up to 8 person

4400 Litres

For up to 14 person

5200 Litres

For for up to 18 person

6800 Litres

For up to 26 person

8400 Litres

For up to 36 person

10,000 Litres

For up to 45 person

Lid options:

Pedestrian duty lockable cover

This is suitable for when the Septic tank is located where no vehicles will need to pass over the tank. It is suitable to withstand pedestrians walking on the lid and is rated to carry a weight up to 200kg.

The underground Septic tanks are designed for shallow-dig installation with a pea gravel surround. However, the installation can be modified to allow vehicles to drive over the tank where required.

Light vehicle cover

View all Washdown separators here

Optional extras:

Telescopic extension risers – allow the depth of the tank to be increased to between 400 and 750mm. This can be easily trimmed by using a hand saw.

Sewage treatment plants

Sewage treatment plants are designed to treat domestic wastewater to a much higher standard than a traditional septic tank, the sewage treatment plant produce cleaner effluent that can typically be discharged to a watercourse or drainage field, subject to local regulations and site conditions.

Tank types:

Harlequin CAP range

These sewage treatment plants are perfect for the treatment of sewage waste and suitable for discharge to both watercourse or drainage field. These come in a compact design and comes with a movable tank compressor box. These have a pollutant removal percentage of 96.2%.

Harlequin HydroClear range

Hydroclear systems come with an energy efficient, super quiet treatment reactor to clean sewage waste to an extremely high degree suitable for discharge to both watercourse and drainage fields. Easy installation and consistent results. Pollutant removal level percentage of 97.5%

Capacity options:

CAP & Hydroclear 6

For 1-6 person

CAP & Hydroclear 9

for 7-9 person

CAP & Hydroclear 12

For 10-12 person

CAP 15

For 13-15 person

CAP 18

For 16-18 person

Hydroclear 30

For 21-30 person

Hydroclear 40

For 31-40 Person

Hydroclear 50

For 41-50 Person

Outlet Options:

Gravity (Standard)

For when the final effluent runs downhill to the water course or drainage field

Integral pumped outlet

For when the effluent needs to be pumped uphill to a watercourse or drainage field.

View all Sewage treatment plants here

Optional extras:

Low pressure alarm – provides an early warning if the blower pressure drops, helping to identify issues before they affect the performance.

Washdown Separators

Washdown separators are designed to remove silt, sediment, oils and hydrocarbons from contaminated wash water before it enters the drainage system.

Our washdown separators are suitable for a wide range of commercial and agricultural applications, including:

Capacity options:

1800 Litres

Designed for single jet wash and hand wash applications

2600 Litres

Designed for commercial car wash and vehicle cleaning applications

3600 Litre

Designed for commercial vehicle wash and industrial cleaning applications

4400 Litres

Designed for commercial vehicle wash and industrial cleaning applications

5200 Litres

Designed for commercial vehicle wash and industrial cleaning applications

5400 Litres

Designed for commercial and industrial vehicle wash applications

6800 Litres

Designed for brush wash and agricultural equipment cleaning